1. Field of the Invention
The invention relates to a power saving circuit, and more particularly, to a power saving circuit applied in computer systems.
2. Description of the Related Art
In a conventional computer system, all peripheral devices will be waked up when powered on. In other words, all controller chips corresponding to the peripheral devices will also be activated for operation.
However, users may not utilize all of the computer peripheral devices all the time or users may only utilize some computer peripheral devices during a specific time period. The peripheral devices which are not frequently used and controller chips corresponding thereto, however, still consume power, thus causing the conventional computer systems to inefficiently utilize and waste power.
Five ACPI (Advanced Configuration and Power Interface) states, such as S0, S1, S3, S4 and S5 states, are commonly utilized in computer systems. However, computer systems can only normally operate in the S0 state, while computer systems enter a sleep state in the S1-S5 states. Thus, while computer system power can be saved, computer system operation is inconvenient.